return true;
    }

    @Override
    public Iterator<Entry<K, V>> iterator() {
      return entrySetIterator();
    }

    // See java.util.Collections.CheckedEntrySet for details on attacks.

    @Override
    public @Nullable Object[] toArray() {
      return standardToArray();
    }

    @Override
    @SuppressWarnings("nullness") // bug in our checker's handling of toArray signatures

      return true;
    }

    @Override
    public Iterator<Entry<K, V>> iterator() {
      return entrySetIterator();
    }

    // See java.util.Collections.CheckedEntrySet for details on attacks.

    @Override
    public @Nullable Object[] toArray() {
      return standardToArray();
    }

    @Override
    @SuppressWarnings("nullness") // bug in our checker's handling of toArray signatures

              return typePreservingCollection(entry.getValue(), mutex);
            }
          };
        }
      };
    }

    // See Collections.CheckedMap.CheckedEntrySet for details on attacks.

    @Override
    public @Nullable Object[] toArray() {
      synchronized (mutex) {
        /*
         * toArrayImpl returns `@Nullable Object[]` rather than `Object[]` but only because it can

      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>build-helper-maven-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-gradle-module-metadata</id>
            <goals>
              <goal>attach-artifact</goal>
            </goals>
            <configuration>
              <artifacts>
                <artifact>
                  <file>target/publish/module.json</file>

      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
      </plugin>
      <plugin>
        <artifactId>maven-source-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-test-sources</id>
            <phase>post-integration-test</phase>
            <goals><goal>test-jar</goal></goals>
          </execution>
        </executions>
      </plugin>
      <plugin>

      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
      </plugin>
      <plugin>
        <artifactId>maven-source-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-test-sources</id>
            <phase>post-integration-test</phase>
            <goals><goal>test-jar</goal></goals>
          </execution>
        </executions>
      </plugin>
      <plugin>

      contents.add(checkNotNull(element), occurrences);
      return this;
    }

    /**
     * Adds or removes the necessary occurrences of an element such that the element attains the
     * desired count.
     *
     * @param element the element to add or remove occurrences of
     * @param count the desired count of the element in this multiset
     * @return this {@code Builder} object

   * the discussion in the {@link #addListener} documentation. All its warnings about heavyweight
   * listeners are also applicable to heavyweight callbacks passed to this method.
   *
   * <p>For a more general interface to attach a completion listener, see {@link #addListener}.
   *
   * <p>This method is similar to {@link java.util.concurrent.CompletableFuture#whenComplete} and

 * passing in unsanitized user data then a malicious user could force it. A light shuffle of the
 * data using an unpredictable seed should normally be enough to thwart this attack.
 *
 * <p>The time taken to compute multiple quantiles on the same dataset using {@link Scale#indexes
 * indexes} is generally less than the total time taken to compute each of them separately, and

  @CheckForNull private transient Node<K, V> tail; // the tail for all keys
  private transient Map<K, KeyList<K, V>> keyToKeyList;
  private transient int size;

  /*
   * Tracks modifications to keyToKeyList so that addition or removal of keys invalidates
   * preexisting iterators. This does *not* track simple additions and removals of values